Surgical microscopes provide a magnified view of the operating field to the surgeon. Ophthalmic surgical microscopes are commonly stereo zoom microscopes with binocular view ports for the surgeon, and frequently have one or two observer view ports at ninety degrees (left and right) to the surgeon. The working distance between the objective lens of the microscope and the surface of a patient eye may range from about 100 mm to about 200 mm in order to allow the surgeon sufficient working area.
Surgical microscopes are tailored to provide clear optical view to the subject, with uniform illumination and accurate color temperature. Stereo microscopes provide a degree of parallax to provide the surgeon with a sense of space and topography. Occasionally dyes are used to emphasize topography. High definition video is being offered into surgical microscopes to improve visual clarity. Topographic 3D video technologies adopted from entertainment industry, such as polarization-diversity stereoscopy, are now being added to increase the sense of depth.
Such surgical stereo microscopes are constrained to surface visualization. Optical coherence tomography (OCT) is now a well-established technology for imaging beneath an optically translucent surface. High resolution OCT offers a capability to observe sub-surface structures, complementary to the surface views of stereo, high definition and 3D surgical microscopes. Optical coherence tomography is a standard of care in retinal diagnostics, and is finding some use in cornea imaging and metrology OCT is only beginning to find use in intra-surgical imaging. Bioptigen offers a handheld ophthalmic OCT system has been FDA cleared for imaging patients under anesthesia. This device is finding application in handheld and mounted configurations for structural imaging during ophthalmic surgeries, including retinal surgery and cornea transplant surgery and an adjunct to surgeon's microscope visualization.
OCT is now incorporated in certain ophthalmic surgical laser systems. OCT is incorporated in LensX and Optimedica femtosecond laser assisted cataract (FLAC) surgical systems to provide ranging to the crystalline lens as a guidance device to facilitate focus of the surgical laser. At present, this ranging function is the limit of the application of the OCT to the surgical procedure.